This code supports on over-the-wire serialization where the payload is normally very small (10s of bytes) but the maximum is 2^32 bytes.

description.markdown

A length < 255 is encoded using only uint(8), and thus requires only one byte of overhead.

A length > 254 is encoded using a marker byte (255) followed by the length using uint(32), requiring 5 bytes of overhead

OptimizedVariableSizeCodec.scala

 val size: Codec[Int] = new Codec[Int] {
    private val marker = 255
    override def sizeBound = uint(8).sizeBound | uint(32).sizeBound
    override def encode(value: Int) = if (value < marker)
      uint(8).encode(value)
    else
      (uint(8) ~ uint(32)).encode(marker ~ value)
    override def decode(bits: BitVector) = {
      uint(8).decode(bits) match {
        case Attempt.Successful(DecodeResult(value, remainder)) if value == marker => int(32).decode(remainder)
        case _@ x => x
      }
    }
  }

def body[T](contents: Codec[T]) = variableSizeBytes(size, contents)